The invention relates to a cartridge having an electrothermal ignition device.
Significantly greater acceleration effects can be achieved for projectiles fired from guns with the use of high-energy propellant-charge powders, particularly NENA propellant-charge powder (NENA=N(2-nitroxy)nitraminethane) or DNDA propellant-charge powder (DNDA=dinitro-diaza-alkanes), than with conventional propellant-charge powders. Typically, the firing-gas temperature of such propellant-charge powders, and thus the barrel erosion, are lower than with other known powders. The high activation energy of the high-energy propellant-charge powders, however, impedes ignition with the aid of pyrotechnical ignition charges. The reduced ignitability of the propellant-charge powder also leads to an increase in the ignition delay times, and an increased scattering of the ignition times.
To assure a reliable, rapid ignition of a cartridge, e.g., with NENA propellant-charge powder, it has proven advantageous to employ an electrothermal ignition device instead of a pyrotechnical ignition charge. In this case, a high current flows through a wire-type conductor in the floor-side region of the corresponding cartridge such that the conductor vaporizes explosively and generates a high-energy arc. This arc then ignites the corresponding propellant-charge powder.
As the Applicant""s experiments have revealed, in this type of electrothermal ignition device, the relatively heavy dependency of NENA propellant-charge powder on temperature, which leads to a corresponding dependency on the acceleration effect, can be compensated with the quantity of electrical energy supplied to the plasma-ignition system.
A drawback of this electrothermal ignition device is that the generation of the floor-side or base-side arc only effects the ignition of a relatively small percentage of the propellant-charge powder, and, often, no reproducible combustion behavior of the propellant-charge powder results, This is particularly true with propellant-charge powders that are difficult to ignite.
To obtain a reproducible combustion behavior of the propellant-charge powder, German patent Application DE 199 21 379.8, corresponding with Patent Application GB 2,349,940, published Nov. 15, 2000, proposes disposing the wire-type conductors inside tubes also comprising propellant-charge powder extending through the propellant charge, rather than leading the wire-type conductors directly through the propellant-charge. These propellant-charge-powder tubes then constitute ignition conduits inside the propellant-charge structure. In the activation of the ignition device, first the wire-type conductor vaporizes and an arc plasma conduit forms inside the respective propellant-charge-powder tubes. Radiation-transport mechanisms transport the energy to the environment by way of the plasma conduits. This energy transport leads to a rapid ignition of the propellant-charge-powder tubes and their fragmentation. The burning fragments (hot spots) of the propellant-charge-powder tubes, and the released arc radiation, effect a rapid, uniform ignition of the propellant-charge structure.
It has been seen, however, that, in the use of propellant-charge-powder tubes comprising graphitized propellant-charge powder, which is widely available commercially, a relatively large amount of electrical energy is necessary for attaining an adequate ignition interaction with the propellant-charge powder.
In view of the not-previously-published German patent application document DE 199 21 379.8, it is the object of the invention to disclose a cartridge in which even propellant-charge powders that are difficult to ignite, particularly NENA or DNDA propellant-charge powders, can be ignited rapidly and reliably with the smallest possible requirement of electrical energy.
The above object generally is achieved according to the present invention by a cartridge with an electrothermal ignition device, which comprises a cartridge including a combustible sleeve that is at least partially filled with a first propellant-charge powder, and a metal base connected to one end of the sleeve and forming the base of the cartridge. A high-voltage electrode extends through and is insulated from the base, and an electrically-conductive wire, which extends axially through the first propellant-charge powder, has a first end connected to the high-voltage electrode and a second end connected to an electrical contact disposed in the forward region of the propellant-charge sleeve for contacting the inner wall of a gun barrel when the cartridge is fired. The electrically-conductive wire is guided axially through a tube that is formed of a second propellant-charge powder and that is disposed in the first propellant charge powder along at least an axial portion of the propellant-charge sleeve. The second propellant-charge powder forming the tube is an optically transparent propellant-charge powder.
Further advantageous embodiments of the invention are disclosed.
The invention is essentially based on the concept of using transparent propellant-charge-powder tubes. Nitrocellulose powder, particularly the type known as JA2, has proven especially effective as a propellant-charge powder. To assure the transparency of this propellant-charge powder, it cannot contain any black components, and the conventional graphitization of the outside surface must be omitted.
The use of optically transparent propellant-charge-powder tubes permits the radiation emitted by the plasma conduits to reach the propellant-charge structure of the cartridge without large absorption losses. Furthermore, the plasma radiation effects a change in the combustible surface of the transparent propellant-charge-powder tubes, which leads to a significantly accelerated conversion of the tubes, and thus supports the ignition process. The utilization of these properties results in a distinct reduction in the requirement of electrical energy for the plasma-ignition system.
It has also been seen that, with the use of optically transparent propellant-charge-powder tubes, the requirement for additional electrical energy for the temperature compensation of the NENA propellant-charge powder is reduced in comparison to that of non-transparent tubes.
With the use of DNDA propellant-charge powder, this additional electrical energy can be omitted, because the DNDA propellant-charge powder burns extensively independently of the temperature.
Further details and advantages of the invention ensue from the exemplary embodiment described below in conjunction with drawing figures.